Charged-Particle-Beam Processing Using a Cluster Source

ABSTRACT

A cluster source is used to assist charged particle beam processing. For example, a protective layer is applied using a cluster source and a precursor gas. The large mass of the cluster and the low energy per atom or molecule in the cluster restricts damage to within a few nanometers of the surface. Fullerenes or clusters of fullerenes, bismuth, gold or Xe can be used with a precursor gas to deposit material onto a surface, or can be used with an etchant gas to etch the surface. Clusters can also be used to deposit material directly onto the surface to form a protective layer for charged particle beam processing or to provide energy to activate an etchant gas.

The present application is a divisional application of U.S. patentapplication Ser. No. 11/590,570 filed Oct. 31, 2006, which isincorporated by reference.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to charged-particle-beam processing.

BACKGROUND OF THE INVENTION

Charged-particle beams, such as ion beams and electron beams, are usedfor processing work pieces in nanotechnology because charged-particlebeams can form very small spots. For example, focused ion beam systemsare able to image, mill, deposit, and analyze with sub-micron precision.Focused ion beam systems are commercially available, for example, fromFEI Company, Hillsboro, Oreg., the assignee of the present application.The ions can be used to sputter, that is, physically eject, materialfrom a work piece to produce features, such as trenches, in the workpiece. An ion beam can also be used to activate an etchant gas toenhance sputtering, or to decompose a precursor gas to deposit materialnear the beam impact point. An ion beam can also be used to form animage of the work piece, by collecting secondary particles ejected bythe impact of the ion beam. The number of secondary particles ejectedfrom each point on the surface is used to determine the brightness ofthe image at a corresponding point on the image. Focused ion beams areoften used in the semiconductor industry. In one application, forexample, a focused ion beam is used to cut a small trench into anintegrated circuit to expose a cross section of a vertical structure forobservation or measurement using an ion beam or an electron beam.

Electron beams can also be used to process a work piece. Electron beamprocessing is described, for example in U.S. Pat. No. 6,753,538 to Mucilet al. for “Electron Beam Processing.” Electron beams are more commonlyused for forming images in a process called electron microscopy.Electron microscopy provides significantly higher resolution and greaterdepth of focus than optical microscopy. In a scanning electronmicroscope (SEM), a primary electron beam is focused to a fine spot thatscans the surface to be observed. Secondary electrons are emitted fromthe surface as it is impacted by the primary beam. The secondaryelectrons are detected, and an image is formed, with the brightness ateach point of the image being determined by the number of secondaryelectrons detected when the beam impacts a corresponding point on thesurface.

In a transmission electron microscope (TEM), a broad electron beamimpacts the sample and electrons that are transmitted through the sampleare focused to form an image of the sample. The sample must besufficiently thin to allow many of the electrons in the primary beam totravel though the sample and exit on the opposite site. Samples aretypically thinned to a thickness of less than 100 nm. One method ofpreparing samples includes using a focused ion beam to cut a thin samplefrom a work piece, and then using the ion beam to thin the sample.

In a scanning transmission electron microscope (STEM), a primaryelectron beam is focused to a fine spot, and the spot is scanned acrossthe sample surface. Electrons that are transmitted through the workpiece are collected by an electron detector on the far side of thesample, and the intensity of each point on the image corresponds to thenumber of electrons collected as the primary beam impacts acorresponding point on the surface.

When a charged-particle beam impacts a surface, there is the potentialfor damage or alteration of the surface. Focused ion beam systemstypically use gallium ions from liquid metal gallium ion source. Galliumions are relatively heavy, and a gallium ion accelerated through atypical 30,000 volts will inevitably alter the work piece surface.Plasma ion systems, such as the one described in WO20050081940 of Kelleret al. for a “Magnetically Enhanced, Inductively Coupled, Plasma Sourcefor a Focused Ion Beam System,” which is hereby incorporated byreference, can use lighter ions, which cause less damage, but the ionswill still typically alter the work piece surface. Electrons, while muchlighter than ions, can also alter a work surface. When a user desires tomeasure a work piece with an accuracy of nanometers, changes in the workpiece caused by the impact of charged particles can be significant,especially in softer materials, such as photoresist and low-k andultra-low-k dielectric materials, such as polyphenylene materials.

Currently, technicians quantify the dimensional change that is caused bythe charged-particle beam deposition of the protective layer, and thenapply a correction factor to subsequent measurements to obtain anestimate of the true dimension. Such estimates are not always accuratebecause of the variation in the alteration by the charged-particle beam.

When a user desires to use an ion beam to extract a sample viewing witha TEM, as described for example, in U.S. Pat. No. 5,270,552 to Ohnishi,et al. “Method for Separating Specimen and Method for Analyzing theSpecimen Separated by the Specimen Separating Method,” the usertypically scans the focused ion beam in an imaging mode to locate theregion of interest. The scanning causes damage to the surface. When theregion of interest is located and the beam begins to mill a trench,there is additional damage to the work piece because the edges of thebeam are not perfectly sharp. That is, the beam is typically Gaussianshaped, and the ions in the tail of the Gaussian distribution willdamage the work piece at the edge of the trench. Damage has been foundnot just on fragile materials, but also on relatively hard materials.

To protect the work piece surface, it is common to apply a protectivelayer before charged-particle-beam processing. One method of applying aprotective layer is charged-particle-beam deposition, that is, using acharged-particle beam to provide energy to decompose a gas to deposit amaterial on the surface. The protective layer shields the area aroundthe cut and preserves the characteristics of the features that are to beimaged and measured. Commonly used deposition gasses include precursorcompounds that decompose to deposit tungsten, platinum, gold, andcarbon. For example, tungsten hexacarbonyl can be used to deposittungsten, methylcyclopentadienyl trimethyl platinum can be used todeposit platinum, and styrene can be used to deposit carbon. Precursorgases to deposit many different materials are known in the art. Thepreferred material to be deposited as a protective layer depends on theapplication, including the composition of the underlying target surface,and the interaction between the protective layer material and the targetsurface.

Although charged-particle-beam-assisted deposition can locally apply alayer at the precise location where the layer is needed, applying aprotective layer using charged-particle beam deposition has severaldisadvantages. Charged-particle-beam-assisted deposition is relativelyslow and, in some processes, up to sixty percent of the total processingtime is consumed in deposition of the protective layer. When an ion beamis initially scanned onto the target surface to deposit material, thebeam sputters material away from the surface for an initial period oftime until a sufficient amount of deposition material accumulates toshield the surface from the ion beam. Even though that period of timemay be small, it can be large enough to allow a significant amount ofmaterial to be removed, which causes the accuracy of the cross-sectionalanalysis to be compromised.

Electron and laser beams can be used to generate secondary electrons todecompose a precursor gas to deposit a protective layer, but those beamsmay also damage the underlying surface—especially when they are atsufficient energy and/or current density levels for achieving favorableprocessing time. It is generally not practical to use such beams becausedeposition will be too slow if the beams are sufficiently “weak” toavoid harm to the underlying surface. Physical vapor deposition (“PVD”)sputter methods could be used to deposit protective layers in someapplications, but they normally cannot be utilized for productioncontrol applications in wafer fabrication facilities because suchmethods cannot be used to locally apply a deposition layer onto atargeted part of the wafer surface. U.S. Pat. App. No. 60/773,396, whichis assigned to the assignees of the present invention, describes amethod of PVD that can provide a localized layer. A charged-particlebeam is used to sputter material from a target onto the surface. Thecharged-particle beam is not directed to the surface itself and damageis avoided. This method, however, is time consuming.

Another method of applying a protective coating is described is U.S.Pat. No. 6,926,935 to Arjavec et al. for “Proximity Deposition.” In thismethod, the charged-particle beam is not directed at the area ofinterest, but to a region outside the area of interest. Secondaryelectrons decompose the precursor gas over the area of interest toprovide a protective layer. As the protective layer is being createdaround the edge of the region of interest, the charged-particle beam canbe moved inward. This method is also time consuming.

Colloidal silver applied with a brush has long been used to produce aconductive protective layer in scanning electron microscopy. The silverparticles used are relatively large. Using a brush to apply the layercan damage the substrate and cannot provide a localized layer.

Another method of applying a protective coating is to use a felt tippen, such as a Sharpie brand pen from the Sanford division of Rubbermaidcorporation. The ink from a Sharpie pen is suitable for use in a vacuumchamber, because it dries thoroughly, and there is little outgassing inthe vacuum chamber. Touching the pen to the region of interest wouldalter the surface, so the ink is applied near the region of interest,and the ink then wicks onto the region of interest. Compounds in the inkprotect some surfaces. The area affected by the felt tip is very largecompared to the sub-micron features of modern integrated circuits, andthe positioning accuracy of the ink is insufficient.

Applying a protective layer of fullerene molecules for computer diskdrive components is described, for example, in U.S. Pat. No. 6,743,481to Hoehn et al. for “Process for Production of Ultrathin ProtectiveOvercoats” and U.S. Pat. Pub. No. 20020031615 of Dykes et al. for“Process for Production of Ultrathin Protective Overcoats.” Fullerenesare ejected from a source by the impact of an ion beam or an electronbeam, and some of the fullerenes are ejected in the direction of thetarget and coat it.

The industry needs a method of rapidly and accurately applying alocalized protective layer without damaging a work piece surface.

SUMMARY OF THE INVENTION

An object of the invention is to deposit onto or etch a work piecesurface using a cluster beam to reduce surface damage.

This invention includes using a cluster ion source to etch a surface orto deposit material. Using clusters typically reduces substrate damagecompared to using individual ions. The invention is particularly usefulfor depositing a protective layer for charged-particle beam processing.In some embodiments, a precursor gas is decomposed by a cluster beam todeposit a protective layer. In other embodiments, the components of thecluster deposit onto the work piece surface to provide a protectivelayer for charged particle beam processing. Embodiments of the inventionalso include systems that allow for deposition of a protective layerusing a cluster source and for additional charged particle beamprocessing.

The foregoing has outlined rather broadly the features and technicaladvantages of the present invention in order that the detaileddescription of the invention that follows may be better understood.Additional features and advantages of the invention will be describedhereinafter. It should be appreciated by those skilled in the art thatthe conception and specific embodiment disclosed may be readily utilizedas a basis for modifying or designing other structures for carrying outthe same purposes of the present invention. It should also be realizedby those skilled in the art that such equivalent constructions do notdepart from the spirit and scope of the invention as set forth in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more through understanding of the present invention, andadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 shows a preferred embodiment of the invention system including aplasma source that is capable of generating charged clusters of atomsand directing the clusters toward a sample.

FIG. 2 shows a preferred method in accordance with the invention.

FIG. 3 shows a preferred plasma cluster source.

FIG. 4 shows an alternative cluster source.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following is a detailed description of example embodiments of theinvention depicted in the accompanying drawings. The example embodimentsare in such detail as to clearly communicate the invention. However, theamount of detail offered is not intended to limit the anticipatedvariations of embodiments; but, on the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the present invention as defined by the appendedclaims. The detailed descriptions below are designed to make suchembodiments obvious to a person of ordinary skill in the art.

In some embodiments of the invention, a cluster beam provides energy todecompose a precursor gas to deposit a layer, while minimizing damage tothe work piece surface. The cluster beam can also be used to etch thework piece surface, optionally with an etch-enhancing gas. In otherembodiments, a cluster beam directly deposits a protective layer forcharged particle beam processing, preferably the protective layerdeposition and the charged particle beam processing occurring in thesame vacuum chamber.

FIG. 1 shows a simplified illustration of an embodiment of the inventionthat comprises a charged particle beam system 100 including a clusterion source 102, a gas injection system 104, and preferably an electronbeam column 106. A gas injection system is described, for example, inU.S. Pat. No. 5,851,413 to Casella et al. for “Gas Delivery Systems forParticle Beam Processing,” assigned to the assignee of the presentinvention. Another gas delivery system is described in U.S. Pat. No.5,435,850 to Rasmussen for a “Gas Injection System,” also assigned tothe assignee of the present invention. Cluster source 102 provides abeam 108 of clusters of atoms or molecules directed toward a region ofinterest 110 on a work piece 112, which is positioned within a vacuumchamber 114 on a stage 116 (not shown), preferably capable of moving inat least two directions.

FIG. 2 shows a preferred process in accordance with the invention. Instep 210, a work piece is inserted into vacuum chamber 114. In step 212,a portion of the work piece 112 is imaged using the electron beam column106 to locate markings on the work piece surface to register thecoordinate system of the stage 116 with the coordinate system of thework piece 112 so that the stage 116 can be moved to position region ofinterest 110 within an area toward to which the cluster beam can bedirected. In step 214, a jet of a precursor gas is directed toward thework piece 112 in the vicinity of the region of interest 110. Manydeposition precursor gases are known, including tetramethylorthosilane(TMOS), tetraethylorthosilane (TEOS), tetrabutoxysilane Si(OC₄ H₉),dimethyl acetylacetonate gold, organometallic compounds, such astungsten hexacarbonyl (W(CO)₆), and methylcyclopentadienyl trimethylplatinum (C₉H₁₆Pt).

In step 216, the beam of clusters is directed to the work piece surfaceto provide energy to decompose the precursor gas and deposit aprotective layer. Clusters of different types of atoms or molecules canbe used with the invention. The term “cluster” includes groups ofmultiple molecules or atoms. For example carbon in the form offullerenes (e.g., C₆₀, C₇₀, C₈₀ , or C₈₄), gold (Au₃), bismuth (Bi₃),and xenon (Xe₄₀) and other clusters are useful for deposition oretching. The term “cluster” includes not only groups of multiplefullerenes, but also single fullerene molecules which are considered asclusters of carbon atoms. Because each cluster has only one or a fewunbalanced electric charges, the charge-to-mass ratio of the clusterscan be significantly less than the charge-to-mass ratio of individualatoms or molecules used in charged-particle beams. Although the energyof the entire cluster can be relatively large, for example, severalhundred to several thousand electron volts, the energy per component islow.

A typical protective layer is preferably between 0.05 μm and 1 μm thick,more preferably between 0.1 μm and 0.8 μm thick, and most preferablyabout 0.2 μm thick. A preferred protective layer is sufficientlyconductive to dissipate any electrical charge produced by the impact ofthe charged-particle beam onto the work piece. A preferred protectivelayer is “vacuum friendly,” that is, it does not “outgas” or continue toevaporate in a vacuum chamber to interfere with the charged-particlebeam or contaminate the work piece. A preferred protective layerstabilizes the structures on the work piece. The preferred protectivelayer does not interact with or alter the structures on the work pieceand provides mechanical strength so that the dimensions of structureschange little or not at all under the impact of the charged-particlebeam. The deposition is limited to areas near the impact point of thecluster beam.

Because the clusters have masses that are greater than that of thegallium ions in a typical prior art method, damage to the work piece isconfined to surface layer that is thinner than the damage layer causedby a beam of gallium ions. Depending on composition, morphology, andsize of clusters used, and the accelerating voltage, damage to thesubstrate can be confined within the top 20 nm, the top 10 nm, the top 5nm or the top 2 nm. For example, using a 15 kV accelerating voltage forclusters of C₆₀, Au, or Bi clusters would typically limit damage to thetop 5 nm of the work piece. By comparison, a typical gallium ion beamdamages the surface to a depth of about 30 nm to 50 nm. The preferredaccelerating voltage can vary with the type of clusters and the materialof the work piece.

In some embodiments, the protective layer can be composed of thematerial from the clusters, such as a carbon layer deposited fromfullerenes, and in such embodiments a deposition precursor gas isunnecessary. That is, the clusters directly deposit onto the work piece.In other embodiments, the protective layer is composed of decompositionproducts from the precursor gas. In other embodiments, a combination ofthe material in the cluster beam and decomposition products of aprecursor gas are deposited.

In step 218, the region of interest, protected by the protection layer,is processed by a charged particle beam. For example, the region ofinterest can be viewed using scanning electron microscopy, or the regioncan be etched, or an additional material can be deposited using an ionbeam. If a multi-source system is used as the source of the clusterbeam, the plasma material that was the source of the clusters can beremoved from the plasma chamber, and the plasma chamber can be filledwith a different gas for performing a material removal process or amaterial deposition process, with or without an etch-enhancing gas or aprecursor gas being directed to the region of interest. An example of amulti-source system is described in U.S. Prov. Pat. App. 60/830,978filed Jul. 14, 2006 for “A Multi-Source Plasma Focused Ion Beam System,”which is hereby incorporated by reference and which is assigned to theassignee of the present invention.

In other embodiments, an etch-enhancing gas can be used, and the beam ofclusters provides energy to initiate a chemical reaction to etch thework piece with reduced damage outside of the etched area. Etchenghacing gases include XeF2, F2, C12, Br2, I2, fluorocarbons, such astrifluoro acetamide and trifluoroacetic acid and trichloroacetic acid,water, ammonia, and oxygen.

A preferred implementation of the invention uses a plasma source asdescribed in U.S. Pat. App. Pub. No. 2005/0183667 for a “MagneticallyEnhanced, Inductively Coupled Plasma Source for a Focused Ion BeamSystem,” which is hereby incorporated by reference. Such an ion sourceprovides a beam having very low chromatic aberration and can be focusedto a relatively small spot at a relatively high beam current, making itsuitable for precise micromachining and deposition. Such a source canprovide beams of clusters, as well as beams of individual atoms andmolecules for charged particle beam processing. For example, a clusterbeam can be used to deposit a protective layer, and then an argon beamcan be used with xenon difuoride to micromachine a feature in the workpiece.

FIG. 3 shows a simplified schematic diagram of a preferred RF excited,plasma ion chamber. A ceramic plasma ion chamber 300 is wrapped by acoil 302. The coil is excited by an RF source(not shown). Ceramic plasmaion chamber 300 is a cylinder with aperture electrodes 304 at one end.The aperture electrodes exhibit an aperture centered on the cylinderaxis of ceramic plasma ion chamber 300. An ion beam leaves ceramicplasma ion chamber 300 through the aperture of the electrodes 304 andpasses through an ion beam focusing column 306 to produce a deflectablefocused ion beam 308.

Ceramic plasma ion chamber 300 receives, through a valve 309, gas fromone or more of a plurality of sources 310, 312, 314. Sources maycomprise cluster gases, such as those described above, inert gases suchas xenon (Xe) or helium (He), reactive gases such as oxygen (O₂), orprecursor or etch-enhancing gases as described above. Valve 309 may beprovided to select in sequence each of a plurality of different gasesfrom the sources. Thus, one may choose one ion species for milling oretching and choose a second different ion species for deposition.

The source is convenient in that one material can be provided to theplasma source to produce a beam of clusters to provide a protectivelayer, and then a second material can be provided to the plasma sourcefor further processing of the work piece. For example, one may introducea gas containing C₆₀ to decompose a precursor gas to deposit aprotective layer, and then introduce a gas such as Xe for sputtering.

FIG. 4 shows a schematic of an alternative embodiment of a clustersource 400. The cluster source 400 can be in its own vacuum chamber, orcan be in a vacuum chamber that includes one or more additional chargedparticle beam columns, such as focused ion beam columns, e.g., liquidmetal or plasma source columns, or electron beam columns. Thenon-cluster sources can be used, for example, to process a work pieceafter a protective layer is applied using the cluster source. The vacuumchamber can include a gas injection system to direct a depositionprecursor gas or an etch-enhancing gas toward the work piece.

Cluster source 400 includes a crucible 402 containing a source material404. A power source 408 heats a heating coil 410 to provide energy toevaporate source material 404. Evaporated atoms or molecules of sourcematerial 404, referred to generally as components, expand through anozzle 420, which causes the atoms or molecules to condense intoclusters 422. Clusters are preferably loosely bound groups of atoms ormolecules. The components preferably do not form a crystalline structurein the clusters, but are amorphous, resembling a liquid state.Components can also be evaporated by a laser or a beam of electrons orions.

The clusters 422 are charged in an ionizer 430, which may, for example,include an electron source 432 having an electrical potential toaccelerate electrons 434 toward an electrode 436. The electrons 434collide with clusters 422, ionizing some of the components. Typicallyonly a small number of components, such as one or two, are ionized, sothat the electrical charge on each cluster is small. The clusters areoptionally passed though a mass filter 440, which may use a combinationof electrostatic fields, magnetic fields, and apertures so that a beamof cluster 442 having masses in a desired range exit the mass filter 440and are directed toward the work piece 450 Skilled persons willrecognize that the cluster source described in FIG. 4 is simplified, andthat many variations and improvements are known and used.

Such cluster sources have been used, for example, to provide coating foroptical components. A typical cluster from the source of FIG. 4 includesbetween 2 and 10,000 atoms or molecules. The components of a cluster maybe loosely bound to each other, although components in some clusters,such as the carbon atoms in fullerenes, are more strongly bound. Anefficient cluster source produces a relatively large number of clustersof the desired size, compared to the number of unattached components orclusters of undesirable sizes that are produced. Clusters are chargedand typically directed toward the target by electrostatic forces.Because the components can be loosely bound in the cluster, the energyof the cluster can cause it to disintegrate upon impact and allow thecomponents to spread out into a relatively thin, uniform layer on thesurface.

Cluster ion sources, including those using C₆₀, have been used insecondary mass ion spectroscopy to eject material from the surface of awork piece. The low energy per component insures that little momentum istransferred to individual atoms and molecules in the work piece,resulting in very little mixing of the work piece material.

The term charged-particle-beam “processing” as used herein includesimaging, as well as sputtering, etching and depositing.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the invention as defined by the appended claims. Moreover, thescope of the present application is not intended to be limited to theparticular embodiments of the process, machine, manufacture, compositionof matter, means, methods and steps described in the specification. Asone of ordinary skill in the art will readily appreciate from thedisclosure of the present invention, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein may be utilized according to the present invention.Accordingly, the appended claims are intended to include within theirscope such processes, machines, manufacture, compositions of matter,means, methods, or steps. We claim as follows:

We claim as follows:
 1. A method of charged-particle beam processing,comprising: positioning a work piece in a vacuum chamber; directing anetchant precursor gas toward a work piece, wherein the gas adsorbs tothe surface of the work piece; and directing a beam of charged clusterstoward the work piece, the beam depositing energy into the region ofinterest to induce an etching chemical reaction of the adsorbed etchantprecursor gas at the region of interest.
 2. The method of claim 1 inwhich directing a beam of clusters of atoms or molecules toward a regionof interest comprises directing a beam of clusters of inert atoms ormolecules.
 3. The method of claim 1 in which directing a beam ofclusters of atoms or molecules toward a region of interest comprisesdirecting a beam of clusters of non-reactive atoms or molecules.
 4. Themethod of claim 1 in which directing a beam of clusters of atoms ormolecules toward a region of interest on the work piece includesdirecting a beam of clusters including carbon, gold, bismuth, or xenon.5. The method of claim 1 in which directing a beam of clusters of atomsor molecules toward a region of interest on the work piece includesdirecting a beam of clusters including C₆₀, C₇₀, C₈₀, C₈₄, Au₃, Bi₃, orXe₄₀.
 6. The method of claim 1 in which directing a beam of clusters ofatoms or molecules toward a region of interest on the work pieceincludes directing a beam of clusters having an average of greater than100 components per cluster.
 7. The method of claim 1 in which the gascomprises XeF₂, F₂, Cl₂, Br₂, I₂, a fluorocarbon, trifluoro acetamide,trifluoroacetic acid, trichloroacetic acid, water, ammonia, or oxygen.8. The method of claim 1 further comprising directing a charged particlebeam from a non-cluster source toward the etched region of the workpiece in the vacuum chamber.
 9. The method of claim 1 in which directinga beam of clusters of atoms or molecules toward a region of interest onthe work piece includes directing a beam of clusters from a plasma ionsource.
 10. A method of charged-particle beam processing, comprising:positioning a work piece in a vacuum chamber; providing an etchantprecursor gas at the work piece surface; and directing a beam ofclusters of atoms or molecules toward a region of interest on the workpiece, the etchant precursor gas reacting in the presence of the beam ofclusters to etch the work piece surface.
 11. The method of claim 10 inwhich directing a beam of clusters of atoms or molecules toward a regionof interest on the work piece includes directing a beam of clusters ofinert atoms or molecules.
 12. The method of claim 10 in which directinga beam of clusters of atoms or molecules toward a region of interest onthe work piece includes directing a beam of clusters of non-reactiveatoms or molecules.
 13. The method of claim 10 in which directing a beamof clusters of atoms or molecules toward a region of interest on thework piece includes directing a beam of clusters from an evaporativecluster source.
 14. The method of claim 10 in which directing a beam ofclusters of atoms or molecules toward a region of interest on the workpiece includes directing a beam of clusters including carbon, gold,bismuth, or xenon.
 15. The method of claim 10 in which directing a beamof clusters of atoms or molecules toward a region of interest on thework piece includes directing a beam of clusters from a plasma ionsource.
 16. A charged-particle beam system, comprising: a vacuumchamber; a charged particle beam column for directing a beam of focused,non-clustered particles toward a work piece in the vacuum chamber forprocessing the work piece; a work piece support for supporting a workpiece within the vacuum chamber; a cluster ion source, for directing aprimary beam of charged clusters toward the work piece within the vacuumchamber; and a gas injection system for providing an etchant gas in thevicinity of the region of interest on the work piece, the etchant gasbeing adsorbed onto the surface and undergoing a chemical reaction onlyin the presence of the beam of charged clusters.
 17. Thecharged-particle beam system in claim 16 in which the cluster ion sourceincludes a plasma ion source.
 18. The charged-particle beam system inclaim 17 in which the plasma ion source includes an inductively coupledplasma ion source.
 19. The charged-particle beam system in claim 16 inwhich the cluster ion source includes a source of clusters offullerenes.
 20. The charged-particle beam system in claim 16 in whichthe cluster ion source includes a source of clusters of bismuth, gold,or xenon.